Surge current prevention circuit of microwave oven

Abstract

A surge current prevention circuit of a microwave oven, where a surge relay is turned on or turned off by a predetermined DC voltage supplied by rectification of a predetermined low voltage, such that cost of parts of the surge current prevention circuit becomes low to thereby reduce the manufacturing cost, and electricity can be decreased and operation of the microwave oven can be stabilized by the constant switching operation time of the surge relay.

What is claimed is: 
     
       1. A surge current prevention circuit of a microwave oven having a fan motor to be driven by an externally supplied commercial alternating current to thereby rotate a cooling fan and a surge resistor located at an input side of a high voltage transformer for transforming the commercial alternating current voltage to a predetermined high voltage, the surge current prevention circuit comprising: a surge coil forming a tap at a predetermined position of the fan motor and being excited by a predetermined low voltage supplied therethrough; and   a surge relay for being turned on or turned off by excitation of the surge coil.   
     
     
       2. A surge current prevention circuit of a microwave oven having a fan motor for being driven by an externally supplied commercial alternating current to thereby rotate a cooling fan and a surge resistor formed at an input side of a high voltage transformer for transforming the commercial alternating current voltage to a predetermined high voltage, the surge current prevention circuit comprising: a rectifying unit for forming a tap at a predetermined position of the fan motor and for rectifying a predetermined low voltage supplied therethrough to a predetermined direct current voltage;   a surge coil for being excited by the predetermined direct current voltage supplied from the rectifying unit; and   a surge relay for being turned on or turned off according to excitation of the surge coil.   
     
     
       3. A power supply circuit, comprising: a fan motor being driven by an externally supplied alternating current;   a transformer for transforming said externally supplied alternating current; and   a surge current prevention circuit including a surge resistor located at an input side of said transformer through which said externally supplied alternating current must pass, said surge current prevention circuit including a surge coil forming a tap at a predetermined position of the fan motor and being excited by a predetermined low voltage supplied therethrough, and   a surge relay being turned on or turned off by excitation of the surge coil, said relay selectively shorting said surge resistor.     
     
     
       4. A power supply circuit in accordance with claim 3, further comprising a filtering unit for receiving and filtering said externally supplied alternating current before said current reaches said fan motor, said transformer or said surge current prevention circuit. 
     
     
       5. A power supply circuit, comprising: a fan motor being driven by an externally supplied alternating current;   a transformer for transforming said externally supplied alternating current; and   a surge current prevention circuit including a surge resistor located at an input side of said transformer,   a rectifying unit forming a tap at a predetermined position of the fan motor and rectifying a predetermined low voltage supplied therethrough to a predetermined direct current voltage,   a surge coil for being excited by the predetermined direct current voltage supplied from the rectifying unit, and   a surge relay for being turned on or turned off according to excitation of the surge coil to selectively short said surge resistor.     
     
     
       6. A power supply circuit in accordance with claim 5, further comprising a filtering unit for receiving and filtering said externally supplied alternating current before said current reaches said fan motor, said transformer or said surge current prevention circuit.